1. Field of the Invention
The invention relates to a rechargeable button cell, which contains negative and positive electrodes in the form of tablets separated by a separator and an alkaline electrolyte in a casing which is formed from a lower part in the form of a cup and an upper part in the form of a lid which fits therein, the casing parts being sealed in a gas-tight manner by swaging or crimping with the interposition of a sealing ring.
The invention furthermore relates to a method for manufacturing cells of the type mentioned above.
2. Description of Related Art
Rechargeable button cells and their physical design are known from the document "Rechargeable Batteries in Japan" edited by Y. Miyatake and A. Kozawa, JEC Press Inc., 1977, p. 388-391. In this case, these cells are assembled in such a manner that the positive electrode, which is pressed in the form of a tablet, is inserted into the cell container, alkaline electrolyte is added in a controlled manner, the separator, the negative electrode in the form of a tablet and the lid with the contact spring and sealing ring are positioned above the electrolyte, and the cell is sealed in a gas-tight manner by swaging or crimping the edge of the container over the edge of the lid. During the assembly process described above, it is absolutely essential for the electrodes to be positioned centrally and not to move into an eccentric, offset position as a result of mechanical influences, for example caused by vibration from the feed process on the assembly line. In this case, there is a risk of the separator being moved laterally and, in consequence, of the electrodes being short-circuited, and this can lead to total failure of the electrochemical cell. In addition, if the electrodes are in an eccentric position, there is a risk of it no longer being possible to join the seal and the cell lid centrally which, in the case of automatic assembly with high production rates, leads to damage to the seal and/or to the negative electrode. The latter has a disadvantageous influence on both the sealing properties and the electrical characteristics of the electrochemical cell. This is evident, for example, in an increase in the internal resistance of the cell.